Figure 14: The calculated energy loss function.
Conclusions:
The orthorhombic phase of LiBH4 was found to be suitable
for optoelectronic applications. The contributions of Li, B and H atoms
are noticed for the modes of vibrations between different range of
frequencies, i.e., 0 to 400 cm-1, 1100
to 1300 cm-1 and 2250 -2400 cm-1.
The low frequency modes between the ranges ~ 93- 436
cm-1 were observed due to displacement
of\(\text{\ Li}^{+}\) and \([{\text{BH}4]}^{-}\) atoms. The
bending modes were noted between the ranges ~1054-1305
cm-1 due to motion of B and H atoms. Moreover,
symmetric and antisymmetric stretching modes were found between the
frequency values of ~2303-2401 cm-1due to contribution of H atoms. The calculated values of band gaps of
6.35, 6.81 and 7.58 eV for local, non-local and hybrid functionals
indicate that the studied compound is a wide band gap insulator. The
mechanical analysis reveals that LiBH4 is a brittle material. Optical
analysis also endorsed the value of wide band gap. The plasma frequency
is calculated from the highest peak of loss function at energy value of
13.7 eV.